Conventionally, as a medical radiation image obtaining section, a radiation image detecting apparatus, the so-called flat panel detector (FPD), in which solid state image pickup devices are two-dimensionally arranged, has been known. It is known that such a radiation image detecting apparatus is a direct system one, an indirect system one, or the like. The direct system one directly converts radiation energy into electric charges by using a photo conductive material, such as a-Se (amorphous selenium), as a radiation detecting element, and reads out the electric charges as an electric signal pixel by pixel with two-dimensionally arranged signal reading switch elements, such as TFTs (Thin Film Transistors). The indirect system one converts radiation energy into light with a scintillator or the like, converts the light into electric charges with two-dimensionally arranged photoelectric conversion elements, such as photodiodes, and reads out the electric charges as an electric signal with TFTs or the like.
Then, in recent years, a cassette type radiation image detecting apparatus, which incorporates a battery therein and is driven without using any cables so as to be portable, has been developed (see, for example, Patent Documents 1 to 3). When a radiation image detecting apparatus is configured as described above, radiography having a high degree of freedom, including portable radiography at a patient's bedside and the like, becomes possible.